Frontier Airlines, in a nod to Denver Broncos quarterback Peyton Manning, is offering an 18 percent discount on domestic fares through Thursday. The deal, which began Tuesday, applies for travel through March 12, with blackout dates of Feb. 13-15 and Feb. 17.Manning's verbose scrimmage-line exhortations — which often include "Omaha" and the frantic "Hurry! Hurry!" — occasi...